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Pyelonephritis is an inflammation of the kidney and upper urinary tract that usually results from noncontagious bacterial infection of the bladder (cystitis).


Acute pyelonephritis is most common in adult females but can affect people of either sex and any age. Its onset is usually sudden, with symptoms that often are mistaken as the results of straining the lower back. Pyelonephritis often is complicated by systemic infection. Left untreated or unresolved, it can progress to a chronic condition that lasts for months or years, leading to scarring and possible loss of kidney function.

Causes and symptoms

The most common cause of pyelonephritis is the backward flow (reflux) of infected urine from the bladder to the upper urinary tract. Bacterial infections also may be carried to one or both kidneys through the bloodstream or lymph glands from infection that began in the bladder. Kidney infection sometimes results from urine that becomes stagnant due to obstruction of free urinary flow. A blockage or abnormality of the urinary system, such as those caused by stones, tumors, congenital deformities, or loss of bladder function from nerve disease, increases a person's risk of pyelonephritis. Other risk factors include diabetes mellitus, pregnancy, chronic bladder infections, a history of analgesic abuse, paralysis from spinal cord injury, or tumors. Catheters, tubes, or surgical procedures may also trigger a kidney infection.
The bacteria most likely to cause pyelonephritis are those that normally occur in the feces. Escherichia coli causes about 85% of acute bladder and kidney infections in patients with no obstruction or history of surgical procedures. Klebsiella, Enterobacter, Proteus, or Pseudomonas are other common causes of infection. Once these organisms enter the urinary tract, they cling to the tissues that line the tract and multiply in them.
Symptoms of acute pyelonephritis typically include fever and chills, burning or frequent urination, aching pain on one or both sides of the lower back or abdomen, cloudy or bloody urine, and fatigue. The patient also may have nausea, vomiting, and diarrhea. The flank pain may be extreme. The symptoms of chronic pyelonephritis include weakness, loss of appetite, hypertension, anemia, and protein and blood in the urine.


The diagnosis of pyelonephritis is based on the patient's history, a physical examination, and the results of laboratory and imaging tests. During the physical examination, the doctor will touch (palpate) the patient's abdomen carefully in order to rule out appendicitis or other causes of severe abdominal pain.

Laboratory tests

In addition to collecting urine samples for urinalysis and urine culture and sensitivity tests, the doctor will take a sample of the patient's blood for a blood cell count. If the patient has pyelonephritis, the urine tests will show the presence of white blood cells, and bacteria in the urine. Bacterial counts of 100,000 organisms or higher per milliliter of urine point to a urinary tract infection. The presence of antibodycoated bacteria (ACB) in the urine sample distinguishes kidney infection from bladder infection, because bacteria in the kidney trigger an antibody response that coats the bacteria. The blood cell count usually indicates a sharp increase in the number of white blood cells.

Imaging studies

The doctor may order ultrasound imaging of the kidney area if he or she suspects that there is an obstruction blocking the flow of urine. X rays may demonstrate scarring of the kidneys and ureters resulting from long-standing infection.


Treatment of acute pyelonephritis may require hospitalization if the patient is severely ill or has complications. Therapy most often involves a two- to three-week course of antibiotics, with the first few days of treatment given intravenously. The choice of antibiotic is based on laboratory sensitivity studies. The antibiotics used most often include ciprofloxacin (Cipro), ampicillin (Omnipen), or trimethoprim-sulfamethoxazole (Bactrim, Septra). Several advances in antibiotic therapy have been made in recent years. In 2003, the U.S. Food and Drug Administration (FDA) approved Cipro extended release tablets (Cipro XR) that could be taken once daily for acute uncomplicated pyelonephritis. A study in Europe also showed that a shorter course than that normally used in the United States could eradicate the bacteria that cause the disease. The primary objective of antimicrobial therapy is the permanent eradication of bacteria from the urinary tract. The early symptoms of pyelonephritis usually disappear within 48 to 72 hours of the start of antibacterial treatment. Repeat urine cultures are done in order to evaluate the effectiveness of the medication.
Chronic pyelonephritis may require high doses of antibiotics for as long as six months to clear the infection. Other medications may be given to control fever, nausea, and pain. Patients are encouraged to drink extra fluid to prevent dehydration and increase urine output. Surgery sometimes is necessary if the patient has complications caused by kidney stones or other obstructions, or to eradicate infection. Urine cultures are repeated as part of the follow-up of patients with chronic pyelonephritis. These repeat tests are necessary to evaluate the possibility that the patient's urinary tract is infected with a second organism as well as to assess the patient's response to the antibiotic. Some persons are highly susceptible to reinfection, and a second antibiotic may be necessary to treat the organism.

Key terms

Bacteremia — The presence of bacteria in the bloodstream.
Cystitis — Inflammation of the bladder, usually caused by bacterial infection.
Reflux — The backward flow of a fluid in the body. Pyelonephritis is often associated with the reflux of urine from the bladder to the upper urinary tract.


The prognosis for most patients with acute pyelonephritis is quite good if the infection is caught early and treated promptly. The patient is considered cured if the urine remains sterile for a year. Untreated or recurrent kidney infection can lead to bacterial invasion of the bloodstream (bacteremia), hypertension, chronic pyelonephritis with scarring of the kidneys, and permanent kidney damage. In 2003, a report on long-term follow-up of adults with acute pyelonephritis looked at kidney scarring and resulting complications. Kidney damage that causes complications is rare after 10 to 20 years, even though many women showed renal scarring.


Persons with a history of urinary tract infections should urinate frequently, and drink plenty of fluids at the first sign of infection. Women should void after intercourse which may help flush bacteria from the bladder. Girls should be taught to wipe their genital area from front to back after urinating to avoid getting fecal matter into the opening of the urinary tract.



Jancin, Bruce. "Short-course Cipro for Pyelonephritis: Unapproved Regimen Shows Promise." OB GYN News November 1, 2003: 5.
Mangan, Doreen. "The FDA has Approved Ciprofloxacin Extended Release Tavlets (Cipro XR), a Once-daily Formulation, for the Treatment of Complicated Urinary Tract Infections (cUTIs) and Acute Pyelonephritis (AUP), or Kidney Infection." RN November 2003: 97.
Raz, Paul, et al. "Long-term Follow-up of Women Hospitalized for Acute Pyelonephritis." Clinical Infectious Diseases (October 15, 2003):1014-1017.


American Foundation for Urologic Disease. 1128 N. Charles St., Baltimore, MD 21201. (401) 468-1800.


inflammation of the kidney and renal pelvis; see also pyelitis and nephritis. Called also nephropyelitis.


Inflammation of the renal parenchyma, calyces, and pelvis, particularly due to local bacterial infection.
[pyelo- + G. nephros, kidney, + -itis, inflammation]


/py·elo·ne·phri·tis/ (-nĕ-fri´tis) inflammation of the kidney and its pelvis due to bacterial infection.


Inflammation of the kidney and its pelvis, caused by bacterial infection.

py′e·lo·ne·phrit′ic (-frĭt′ĭk) adj.


Etymology: Gk, pyelos + nephros, kidney, itis, inflammation
a diffuse pyogenic infection of the pelvis and parenchyma of the kidney. Acute pyelonephritis usually results from an infection that ascends from the lower urinary tract to the kidney. Escherichia coli contamination of the urethral meatus is a common cause in females. Infection may spread to the kidney from other locations in the body. The onset of acute pyelonephritis is rapid and characterized by fever, chills, pain in the flank, nausea, and urinary frequency. Urinalysis reveals the presence of bacteria and white blood cells (WBCs). Antimicrobial treatment is continued for 10 days to 2 weeks. Relapse or reinfection is common. Chronic pyelonephritis develops slowly after bacterial infection of the kidney and may progress to renal failure. Most cases are associated with some form of obstruction, such as a stone or a stricture of the ureter. Treatment includes removal of the cause of obstruction and long-term antimicrobial therapy.
observations The onset of symptoms is fairly rapid and is characterized by dull, constant flank pain, chills, and fever. Concomitant signs of a lower urinary tract infection (e.g., urinary frequency and dysuria) occur in about one third of individuals. Clinical symptoms are confirmed by urinalysis, which shows antibody-coated bacteria, bacteriuria, WBC casts, and pyuria; a CBC shows an increase in WBCs. Renal function studies may assist in the diagnosis of chronic disease. The most common complication of acute disease is septic shock and/or chronic pyelonephritis. With chronic disease, there is a 2% to 3% chance of developing end-stage renal failure.
interventions Oral or parenteral antiinfective drugs are used to combat infection. Continuous suppression antiinfective therapy may be used to treat recurrent or chronic infection. Antipyretics are used for fever. Hydration is managed by forcing oral fluids or using IV fluids for those unable to take in adequate oral fluids. Follow-up urine cultures are used to track effectiveness of antiinfective drugs. Surgery is used to drain large collections of pus and to correct underlying obstructions. Placement of a nephrostomy tube may be necessary to promote drainage of urine.
nursing considerations Key nursing goals for acute pyelonephritis are to reduce fever, relieve pain, promote comfort, and prevent complications. Individuals should be encouraged to drink at least 8 glasses of fluids daily even after acute infection subsides. Input and output should be closely monitored and urine should be checked for frequency, consistency, color, and odor. Rest is indicated to reduce fatigue, increase comfort, and allow the body to combat the infection. Education is aimed at teaching the individual about the disease, with a focus on the necessity to continue the full course of antibiotic therapy and to get follow-up urine cultures to ensure that infection is gone. Instruction is also necessary in preventing infection (cleansing perineum, proper wiping technique, adequate fluid intake, and cleansing after sexual activity) and in recognizing and treating early signs of urinary tract infection.
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Acute pyelonephritis


Nephrology Infection of the kidney and ureters Types Reflux nephropathy, acute uncomplicated pyelonephritis, complicated UTI or chronic pyelonephritis Etiology UTIs, cystitis, especially with backflow of urine from the bladder into the ureters or kidney pelvis–vesicoureteric reflux Risk factors Hx of cystitis, renal papillary necrosis, kidney stones, vesicoureteric reflux or obstructive uropathy, Hx of chronic/recurrent UTIs, infection by virulent bacteria; elderly, immunosuppression–eg, AIDS, CA


Inflammation of the renal parenchyma, calyces, and pelvis, particularly due to local bacterial infection.
[pyelo- + G. nephros, kidney, + -itis, inflammation]


Inflammation of the pelvis and of the substance of the kidney. This is usually caused by bacterial infection spreading up from the bladder. Acute pyelonephritis causes high fever, shivering and pain in the loin. Repeated or long-term (chronic) attacks may cause permanent damage to the kidney, with high blood pressure (HYPERTENSION) and eventual kidney failure. The condition is treated with antibiotics.


inflammation of the kidney and renal pelvis (see also pyelitis and nephritis). Clinical signs include pyuria, pain on palpation of the kidney, ureteritis, cystitis and passage of blood-stained urine. Called also nephropyelitis.

contagious bovine pyelonephritis
see contagious bovine pyelonephritis.
porcine pyelonephritis
pyelonephritis caused by Actinobaculum suis. The infection is transmitted by the boar. Signs include dysuria, bloody urine and a short course and a high mortality rate.
References in periodicals archive ?
UTI, particularly pyelonephritis, is mostly caused by an obstruction to the flow of the urine due to either calculus, tumor, stenosis or abscess/ cystitis.
Acute pyelonephritis and renal abscesses in adults--correlating clinical parameters with radiological (computer tomography) severity.
Furthermore, in patients not receiving CAP who develop a non-febrile UTI, initiation of CAP is an option in recognition of the fact that not all cases of pyelonephritis are associated with fevers.
Conclusions: The results of our study show that both F-URS and TPLU are safe and effective surgical procedures for treatment of large proximal ureteral stones after controlling obstructive pyelonephritis.
9) Progressive renal damage from unrecognized pyelonephritis in childhood may lead to hypertension and chronic renal failure in later life.
Pyelonephritis may develop when pathogens ascend to the kidneys passing through the ureters.
The report reviews key players involved in the therapeutics development for Pyelonephritis and enlists all their major and minor projects
It is known that the rate of renal scarring due to recurrent acute pyelonephritis ranges between 25%-40% and recurrent UTI with or without VUR is the cause in 10-25% of the children who develop end stage renal disease (2, 14).
Clinical characteristics of emphysematous pyelonephritis.